This invention relates to winding machines and the invention is particularly applicable to winding machines for winding the filaments of electric lamp bulbs, particularly for the automotive industries.
Basically a winding machine of this nature incorporates a mandrel on which the wire coil of the filament is wound, and a wire guide or pitch mechanism which guides the wire relative to the mandrel so as to provide the necessary pitching of the coil of wire on the mandrel. The arrangement is so driven that the mandrel and wire guide rotate relative to each other to provide the coil while the wire guide additionally moves longitudinally of the mandrel to provide the desired pitch of the coil. It is to be observed that while, in probably the majority of these winding machines, the mandrel is rotated and the wire guide moves purely in the longitudinally direction, it is possible for the mandrel to remain stationary and for the wire guide to be driven with both a longitudinal and rotary motion. It is also possible for the mandrel to move both longitudinally and rotationally while the wire guide remains stationary.
In the more usual winding machines of this kind, the drive to the winding machine is provided, for example, from a single prime mover through various gearing for rotary movements and through the use of cam shafts and cam followers where straight line movements are required particularly for such ancilliary devices as wire cutters, would filament ejectors wire clamping arrangements, tail forming mechanisms and so forth.
With the actual winding and the coil pitch mechanisms, very accurate adjustments are necessary in order to be able to provide the correct number of turns, to take into account the required direction of the tails of the filament, to provide synchronisation between the pitch drive and the winding drive.
Not only is the accuracy necessary for the purposes of the actual winding but in many instances over winding or reverse winding has to be carried out in order that the filament tails shall have the correct angle when they are ejected from the machine. This to a great extent depends upon the resilience of the wire which is being wound and the tension which has been built up during the winding operation.
Further problems arise in that, in order for the filament winding machine to fit into the cycle of a lamp making line, it is necessary that the entire operation of winding a filament should take place, for example, in not more than two seconds. This requires the speed of winding to be built up to a very large figure, for example between 6,000 and 10,000 rpm. This is quite difficult with conventional mechanical drives due to the inertia which is inherent in the gear drive to the various parts of the mechanism.
Accurate adjustment of the required number of winding turns, which may be a combination of forwards and backwards winding for tall control purposes, requires a very high control over the gear ratios which are to be used in the operation. In many occasions the exact number of turns cannot be determined except experimentally and for this it is necessary to carry out a change in the gearing between each experimental operation to determine the exact number of winding turns required by a particular wire. Furthermore, any variation in the number of turns which may be required in producing, for example, a different series of lamps requires further experimentation in further gear changing. The difficulties in mechanically changing gears is increased by the fact that a large number of variations of the ratios may be required and with the necessity of having a very large number of spare gear wheels for this purpose.